PMR communications systems, and TETRA in particular, are suitable for use by emergency services, government agencies, public safety networks and the military where security and reliability of communications is of paramount importance. PMR systems are also used in commercial enterprises, for example in distributed or wide area locations such as large industrial sites, mine environments and the like.
A PMR system often comprises a single main site over which radio communications signals are transmitted from a Base Transceiver Station (BTS). Such a site may be termed a “cell” or “main site” and the operator of such a site may be termed a TETRA Network Operator (TNO). Mobile transceiver units, termed “Mobile Stations (MS)” in the TETRA standard lexicon, receive and transmit radio communications from and to the BTS when in the site/cell coverage area. In common with many radio communication systems, PMR radio systems such as TETRA can suffer from gaps in coverage due to a variety of reasons such as the terrain, intervening structures such as buildings and within buildings or tunnels for example.
There are also known public mobile radio networks, for example cellular telephone networks, operated by so-called Mobile Network Operators (MNO). Cellular telephone networks generally support data communications services and are known as second-generation (2G), third-generation (3G) and fourth-generation (4G) with each later generation providing greater data communications services than the previous generation.
Due to their generally lower operating frequencies and narrower communications channels PMR systems often have better rural coverage than cellular telephone networks, however data bandwidths are invariably lower than can be achieved by the public networks.
Aspects and embodiments of the present invention were devised with the foregoing in mind.